1. Field of the Disclosure
The present disclosure relates to a passive containment spray system that when an accident occurs in a nuclear power plant, sprays coolant passively into a containment, condenses steam discharged from a reactor coolant system or a secondary system of the nuclear power plant, and lowers pressure within the containment.
2. Background of the Disclosure
A nuclear reactor is categorized by a method of configuring a safety system or by an installation position of a main apparatus. First, the nuclear reactor is categorized by the method of configuring the safety system into an active nuclear reactor that uses active force such as one produced by a pump and a passive nuclear reactor that uses passive force such as force of gravity or gas pressure. Then, the nuclear reactor is categorized by the installation position of the main components into a loop type nuclear reactor (for example, a conventional pressurized water reactor) in which the main components (a steam generator, a pressurizer, a pump and the like) are installed outside of a reactor vessel and an integral nuclear reactor (for example a SMART nuclear reactor) in which the main apparatuses are installed within a reactor vessel.
A containment spray system is used as one among systems that suppress an increase in pressure when an accident, such as a loss of coolant accident or a steam line break, that causes an increase in pressure within a containment (a reactor building, a containment vessel, a safeguard vessel and the like may substitute for the containment, the containment building or the reactor building is made up of reinforced concrete, and the containment vessel or the safeguard vessel is made up of steel) occurs in the various nuclear reactors including the integral reactor. Examples of application of an active containment spray system that sprays coolant into the containment using a spray pump is a SMART nuclear reactor of KOREA, a conventional pressurized water reactor, and the like.
In addition to the containment spray system, a suppression tank or pool (a conventional boiling water reactor, U.S.A Westinghouse IRIS), a heat exchange or condenser (France SWR 1000 and India AHWR), a containment external spray and cooling (U.S.A. Westinghouse AP 1000) and the like are used as a system for suppressing the increase in pressure within the containment.
If the pressure within the containment increases due to water(evaporated) or steam discharging, in the suppression tank method, steam and air is introduced into the suppression tank due to a difference in pressure and the steam is condensed, thereby decreasing the pressure. In the heat exchanger method, the steam within the containment is condensed using a cold wall surface of a heat exchanger tube, thereby decreasing the pressure. In the spray method, the cold coolant is sprayed and the steam within the containment is condensed, thereby decreasing the pressure. In addition, in the containment external spray and cooling method, the containment vessel is cooled by spraying the coolant (applying air-cooling later) to an external wall of a steel containment vessel and the steam is condensed on an internal wall, thereby decreasing the pressure within the containment vessel.
An active spray system (internal spraying) is operated by a spray pump is used in many conventional nuclear reactors (active nuclear reactor), and a passive containment spray system (external spraying) is operated by gravity after opening an isolation valve is used in U.S.A. Westinghouse AP 1000 (passive nuclear reactor) and the like.
However, the passive containment spray system in the related art, although it has much advantages as a passive system, includes the isolation value that is operated with a driving electric power source including an operation signal and an electric power source. Thus, if failure to an actuation signal generation system or an electric power system occurs, there is a possibility that the passive containment spray system in the related art will not be operated.